Introduction to Organ systems

We're about to spend some time learning the organ systems of the body. Now, just quickly remember, an organ system is a group of organs that coordinate to perform a common function. Now, we're learning them now because the study of anatomy and physiology, this course the course that you're taking, it's often broken up by these systems. If you look at the chapters in your textbooks, the units of their course, it's usually different organ systems or groups of organ systems here, as we go through them, we're gonna group them by function. And the groups that we do here are pretty common and it's quite often the order that you'll go through them in your course. First off, we're gonna have protection structure and support. That's gonna be the integumentary system, your skin, the skeletal system and the muscular system. Then we'll talk about communication and integration your nervous system and your endocrine systems. We'll talk about transport and immunity, the circulatory or cardiovascular system and the lymphatic system. And as part of the lymphatic system, we'll talk about the immune system. Next, we'll do nutrient gas and waste exchange. That's gonna be your digestive system, your respiratory system and your urinary system sometimes called the respiratory system. And lastly, we'll talk about reproduction. That's gonna be the reproductive system. And each person has one of those systems. But obviously, there's two main variants, the male and female reproductive systems. Now, it's important to remember that bodies are highly integrated. No organ system does its job completely on its own. And organ systems also have many overlapping functions. So as we go through each system, we're gonna list one or two or three of their main functions, almost certainly these systems do other things. We're just trying to hit the big ones right now. And as we list those function, remember, almost certainly it doesn't do it on its own. It can be really hard in the body to draw distinct lines that this does that and this does that. But we still try to group things because we're humans and that's what we like to do. All right. Last thing to know as we go through these different organ systems, we'll be talking about the different organs that belong to each one. You are not expected to know all the organs of the body at this point in the course, but you probably know a lot of organs already. So the ones that you do know, you should start organizing in your head by body systems with that, let's learn some body systems.

We're gonna start our tour of the organ systems by talking about systems that provide protection and support. First off, we have the integumentary system. The integumentary system is your skin, your hair and your nails, your skin, hair and nails provide excellent protection. Your skin provides great protection against friction, right? We're always touching things, rubbing against things. Our clothes are always rubbing on us. Skin is very tough and you probably know if you ever have a place where that skin is worn off, you really don't wanna touch stuff because you don't have that protective barrier. Skin is also providing a waterproof barrier for your body. And it's keeping other just random things from getting in. For example, you're covered in bacteria. If you ever get a cut, you probably put some antibiotic ointment on it because that cut gives away through your anti anti system for the bacteria to get inside your body. The integumentary system is also providing thermal regulation. In other words, it's regulating your body temperature. Now, most mammals, the injury system is doing this with body hair. We don't really use hair that way. The way our integumentary system regulates temperature is through sweat glands and sweat, we cover our body with sweat and then, because we're largely hairless, that evaporates and cools the body. Now, interestingly, we're really the only animals that use sweat in exactly that way. So, next time you are covered and drenched in sweat and feeling disgusting. Remember, it separates you from the animals. All right. Next up, we have the skeletal system. The skeletal system is your bones and your cartilage. And it is there largely to provide structure. The skeletal system is really the only hard stuff in your body without it, you'd be a lump of soft flesh, but your body has shape. It has structure because of the skeletal system. It's also gonna provide protection, right? I can beat on my chest and I don't worry about it because I got a rib cage and a sternum that's protecting my internal organs. If I didn't have that rib cage, I would have just punched my heart repeatedly. And that would have been a really poor choice. Next up, we have the muscular system and the muscular system is gonna provide movement. Muscles are really the only thing in your body that can move on their own, at least on a tissue level, the way they move, they only move one way they get shorter. And so when you flex a muscle, it gets shorter and pulls on things. For this reason, muscles and bones work really closely together. If you didn't have bones in your arm. If you flex your bicep, your arm would just get shorter, but your bones can't get shorter. So instead they work like a lever and they bend. So muscles and bones work really closely together so closely together that sometimes they're taught as one system. Sometimes they're taught as the muscular skeletal system. That's gonna be especially true if you're taking a physiology only class. All right, with that, we have three systems down and I'll see you in the next video.

Up next, we have two systems that provide communication and integration, the nervous system and the endocrine system. And these two systems are most responsible for maintaining homeo stasis in the body. And homeostasis is the maintenance of a stable internal environment. We're not gonna spend a lot of time talking about homeostasis right now, but we're gonna spend a lot of time talking about it going forward. So when we do, you want to keep in mind how these systems function. So both the nervous system and the endocrine system provide communication, but they do it very differently. We'll start with the nervous system. The nervous system is comprised of the brain, the spinal cord and all the nerves of the body and sometimes will include the special senses of the body as well. The nervous system does its communication and integration through rapid communication and integration using electrical signals. When I think of the nervous thinking system, I think of direct point to point communication very, very quickly. If I touch something, a message goes up to my brain and I feel it what feels like to me instantly, it's almost instantly if I want to move a muscle, a signal goes from my brain. It goes to the very specific muscle and my arm moves in a very specific way that's rapid communication using electrical signals. That's in contrast to the endocrine system. The endocrine system is gonna be made of all these different glands. And you don't need to know all the different glands right now. But just know that the endocrine system is made of endocrine glands. These endocrine glands are really good at providing whole body coordination and communication and they do it using chemical messages, messengers called hormones. The endocrine system works by making hormones and putting them into the blood. These chemicals then go through our body because our blood goes everywhere in our body. So the messages from the endocrine system go everywhere. Now, not every cell responds to the message, different cells respond differently and it can take a little while for the blood to get everywhere and for all those responses to happen. So the endocrine, unlike the nervous system will often take well, at least usually minutes for a response to happen. And, and more often in the timeline of hours or maybe even days to finish this off. I'll just give you a little analogy if I think about sending out messages to my friends or people on my college campus. Right? I have a couple of ways that I could do it if I need to send a, send a very specific message to just a few people. I'm gonna send a text message. Right. I'll send them a text message. They'll arrive on their phone immediately. They see it right away. Direct point to point communication, using electrical signals. That is the nervous system. On the other hand, I could put flyers up all over campus announcing something. Everybody is gonna see it. Not, everyone's gonna care different. People are gonna respond differently and it's gonna take them a little longer for everybody to see it. That's much more like the endocrine system. All right, with that, we have two more systems down and I'll see you in the next video.

Here, we have systems that provide transport and immunity. First up, we have the circulatory system also known as the cardiovascular system. All right, the circulatory or cardiovascular system is made up of your heart arteries, capillaries, veins and your blood. Basically, you have a pump your heart that pumps blood through blood vessels. Now, it does that to transport materials to the body. Now, what materials I'm gonna put in parentheses here. 02. Because that's what your blood is most specialized for carrying, that's what red blood cells are for. But your blood is gonna carry all sorts of materials. It's gonna carry waste, it's gonna carry nutrients. It's gonna carry hormones, it's gonna carry water so on and so on. Anything in your body that needs to get from one place in the body to another is probably gonna use the circulatory system to get there. Now, we have a sort of what's sometimes called a secondary circulatory system and that's our lymphatic system. Our lymphatic system is made mostly of lymphatic vessels and those are largely designed to transport water. Your circulatory system lets out a lot of water into the extracellular space of your body. And it starts to collect there and to keep you from blowing up like a water balloon, you have these lymphatic vessels which sort of funnel that water back up and then put it back into the circulatory system. Now, we put here the immune system as part of the lymphatic system. The immune system is kind of funny because it doesn't have a lot of, or it doesn't really have large organs of its own. It's comprised of all these sort of independent cells that are traveling throughout the body. So we put it with the lymphatic system because one way that the immune system travels through the body is through these lymphatic vessels. And there's specialized structures of the lymph system of the lymphatic system that the immune system uses. Those are gonna be lymph nodes, tonsils, thymus and spleen. Basically, these things are places where the immune system can sort of stage fights against infection or be, or be specialized places where they can fight infection. You're probably familiar with. When you get sick, you might get swollen lymph nodes. That's because the immune system is collecting in the lymphatic system to fight an infection. Ok. With that, we've done transport and immunity and I'll see you in the next video.

Now we're gonna talk about systems that perform gas nutrient and waste exchange. What these systems have in common is they exchange material between the outside of the body and the blood before we go on, I just want to think about what we mean. When we say inside and outside the body, you probably think that when you inhale something or eat something, it goes into your body. I want to think about things a little bit differently to be inside your body. Something has to cross into the tissue of your body has to be in the tissue or the blood or the cells of your body. So for example, if you eat a penny, that penny is gonna go into your digestive tract and it'll go down and through your body and it'll come out the other side, but it has no chance of ever getting into the tissues of your body. It has no chance of being in the blood or the cells for our purposes. That penny was never really in your body. It was just kind of traveling through the middle of you. So how do things get in and out of those tissues? Well, the first way is the respiratory system, the respiratory system is gonna be these tubes that lead to the really important thing. The lungs, the lungs is the site of gas exchange and gasses. Chiefly oxygen or 02 and CO2 or carbon dioxide. Oxygen is the major requirement for cell cellular respiration and carbon dioxide. The major waste product. Now, importantly, anything that's in different concentration in the air, in the blood and soluble in both will be exchanged in the lungs. So, for example, that's why a Breathalyzer test works. If a person has alcohol in their blood, while alcohol is soluble in both the blood and the air, it's gonna be in higher concentration in the blood. So when they exhale, it's gonna dissolve into the air come out and be registered by a Breathalyzer test. With that in mind, we'll move on to the digestive system. The digestive system consists of the mouth, the esophagus, the stomach, the small intestines, the large intestines, that's the tube that just goes through you from one end to the other. And then you have some accessory organs, your liver pancreas gallbladder, you could put the salivary glands in there. The function of the digestive system is to obtain water and nutrients from food. The first half of that tube is all about breaking that food up, crushing it, ripping it, getting it wet, we had acids to it. We had enzymes to it, to break it down to its component molecules. And then the second half is all about absorbing it into the blood. Now, you'll know I didn't say remove waste as a major function of the digestive system, that waste of the digestive system that comes out your feces. It's really more like the penny. You eat a lot of food that your body just doesn't use. So it travels through your body but it never has a chance to get into your tissues or your blood. When we think of getting rid of waste, we wanna think of waste generated in the tissues. Very little waste is actually put into the digestive system. The majority of it just stuff that passes through. So how does your body get rid of waste? Well, the first way was the respiratory system, but another way is the urinary system, the urinary system consists of your kidneys, the ureters, which are tubes that connect the kidneys to the bladder and your urethra, which is the tube that connects the bladder to the outside world. The urinary system removes waste and excess water from the blood. The waste is largely urea a nitrogenous waste that gives urine, its characteristic smell and color, but plenty of other waste will be removed as well. Now, in terms of water, your kidneys are responsible for keeping a constant water level in your body. If you drink a big glass of water, that water is gonna be absorbed in the digestive system, it'll enter the blood. Now you have too much water in your blood. The kidneys of the urinary system will take that water out, put it in the urine and you can pass it out of your body. All right. With that three more systems down, I'll see you in the next video.

Finally, we're gonna talk about reproduction. And by that, I mean to produce offspring. Now, every person has only one reproductive system, but it comes in two main flavors, the male reproductive system and the female reproductive system. Let's start with the female reproductive system. Female reproductive system consists of the mammary glands, the ovaries, the uterine tubes, the uterus and the vagina and the female reproductive system has a number of jobs to do. In order to support reproduction. First off, it needs to produce eggs, eggs being the gametes or the sex cells that females produce. Next, it needs to receive the sperm. So the egg can be fertilized, that fertilized egg will implant in the uterus where the female can support fetal development. Of course, once the baby is developed, there will be birth and even after birth, the female can support the baby with milk from the mammary glands. Now, in contrast, the male reproductive system consists largely of the testes, the ductus stri those are the tubes that connect the testes to the urethra, the prostate gland and the penis. The male reproductive system really has one job and that is to produce and deliver sperm to the female and that's the reproductive system. Now, at this point, I think it's important to pick your favorite organ system and to be able to defend why it is your favorite. Now, that's unlikely to be a test question though. I used to ask it on my tests, but it's fun to talk about. I bring this up here because my favorite organ system is the reproductive system. That's because of all the different organ systems. It's the only one where there are fundamental differences between people and think about your life. How much of your life in some way was based on the reproductive system that you were born with. Now, in contrast, you don't need a reproductive system. Of course, people need reproductive systems for their to be people on earth, but you personally can live without one. Plenty of people have their reproductive systems largely removed, whether it's due to cancer or other reasons. And they go on to live normal lives. That contrast a system that you don't need and yet dominates so many aspects of our life. I find that forever fascinating. Now, maybe your favorite system is the digestive system because you really love cookies that's defensible as well. With that. We have finished our tour of the organ systems and I just wanna say good job, everybody.

The digestive and respiratory systems are both responsible for taking in useful molecules into the body. When taken in by these systems, where do the molecules go first?

• A. The muscular system.
• B. The cardiovascular system.
• C. The endocrine system.
• D. The urinary system.

Which system is the least responsible for keeping you alive on a day-to-day basis?

• A. The reproductive system.
• B. The cardiovascular system.
• C. The digestive system.
• D. The endocrine system.

Distinguish between the endocrine system and the nervous system.

• A. The nervous system sends messages using chemical signals, while the endocrine system uses electric signals. 
• B. The endocrine system's communication mechanisms tend to work more slowly than the nervous system.
  
• C. The endocrine system uses direct point-to-point communication; the nervous system sends whole-body messages.
  
• D. Both the systems use hormones, but hormones from the endocrine system enter the blood.

Which two systems allow materials to move from one region of the body to another?

• A. Endocrine and cardiovascular.
• B. Respiratory and digestive.
• C. Digestive and integumentary.
• D. Circulatory and lymphatic.

Which organ systems directly allow waste materials to be passed out of the body?

• A. Respiratory and endocrine.
• B. Circulatory and digestive.
• C. Urinary and respiratory.
• D. Circulatory and lymphatic.

Of all your systems, the integumentary, respiratory, and digestive most regularly experience infection from microorganisms. Which answer best describes why that may be the case?

• A. All three systems are in regular contact with substances from outside the body that may contain bacteria.
• B. All three systems are closely linked to the immune system, meaning they protect against microorganisms.
• C. All three systems have limited blood supply, meaning the body has difficulty fighting infection in those places. 
• D. All three systems function to transfer materials from outside of the body to inside the body, giving microorganisms and entry point.